1. Field of the Invention
The present invention relates generally to roll papers and, more particularly, to a roll paper for a thermal printer for use in a video graphic printer or the like.
2. Description of the Prior Art
Recently, it has been requested that prepaid cards such as telephone cards, commutation tickets, ID (identification) cards and so on can individually record picture and character informations on their surfaces in order to keep a close relationship with money and security. A video graphic printer is known to meet with such requirements. The video graphic printer employs a thermal print head for printing picture and character information on a heat-sensitive coloring paper having a heat-sensitive coloring layer.
FIGS. 1-4 show arrangements of conventional roll papers for a thermal printer, and FIG. 1 shows a perspective view of a roll paper for a thermal printer which is most generally utilized for such video graphic printer.
As shown in FIG. 1, a coloring paper 3 having a thermal coloring layer is stuck on a peeling paper 2 by an adhesive. The resultant paper is rolled around a bobbin or spool 1. This roll paper is fed to a printer (not shown) and picture and character informations are recorded on the coloring paper 3 by a thermal print head.
This roll paper for a thermal printer encounters with a problem. That is, if the coloring paper 3 with the peeling paper 2 stuck thereunder is rolled around the spool 1, then a so-called rolling difference or feeding difference with respect to the axis thereof occurs between the peeling paper 2 and the coloring paper 3, causing wrinkles 4 on the coloring paper 3 as shown in FIG. 1, which results in poor printing.
FIG. 2 is a cross-sectional side view illustrating a portion shown by a circular arrow A in FIG. 1 in an enlarged scale. As shown in FIG. 2, the wrinkle 4 of the coloring paper 3 is raised in a bank shape from the peeling paper 2 in response to the amount of the feeding difference.
In order to solve the aforenoted problems, a roll paper for a thermal printer is proposed as shown in FIGS. 3 and 4.
As shown in FIGS. 3 and 4, starting point detection apertures 5 are bored at a predetermined pitch through the peeling paper 2 along its longitudinal direction. After each of the detection apertures 5, 5, . . . , an image forming portion in which picture and character informations are recorded, that is, a sheet of a substantially rectangular label-like thermal coloring paper 3a having a coloring layer is stuck on the peeling paper 2 by an adhesive (not shown). Then, the peeling paper 2 having the sheet of label-like coloring paper 3a stuck thereon is rolled around the spool 1. If the peeling paper 2 on which the sheet of coloring paper 3a having the thermal coloring layer is stuck as described above is rolled around the spool 1, the occurrence of wrinkles 4 due to the feeding difference in the rolling-process as described with reference to FIGS. 1 and 2 can be avoided and thus the poor printing can also be avoided.
The roll paper for a thermal printer shown in FIGS. 3 and 4 can prevent the wrinkles 4 from being produced upon rolling and thus eliminate the defective printing, but it has the following problem. As shown in FIG. 4, when a thermal print head 6 is brought in contact with the label-like coloring paper 3a on the thermal rolled paper 3 to record picture or character information, the thermal print head 6 touches the edge of the label-like coloring paper 3a upon recording to cause the latter to be peeled off from the peeling paper 2 because there is a level difference 7 between the coloring paper 3a and the peeling paper 2. As a result, a so-called jamming occurs so that picture and character informations cannot be recorded on the coloring paper 3a, and also stripes are formed on the image forming area due to the level difference upon winding, thus causing defective printing.